The Personal Computer Memory Card International Association (PCMCIA) is a standard interface and specification to allow PCMCIA peripheral cards to vary the capabilities of a computer system or other electronic equipment. The PCMCIA peripheral cards consist of a connector that interfaces to a printed circuit board that is approximately the size of a credit card. A typical system of the prior art, including PCMCIA capability, is illustrated in FIG. 1. The main printed circuit board or motherboard 100 includes the central processing unit (CPU) 126 which controls the operations of the computer system and also the internal system memory 128. The CPU 126 is coupled to the system memory 128 and the other integrated circuits on the motherboard 100 by the core logic 124 and the system bus 140.
The PCMCIA Host Adapter integrated circuit 110 is coupled as the interface between the system bus 140 and the PCMCIA expansion slots 112 and 114 in order to control communications between the PCMCIA expansion slots 112 and 114 and the system bus 140. The PCMCIA Host Adapter integrated circuit 110 is coupled to the PCMCIA expansion slot 112 by the PCMCIA interface bus 120 and to the PCMCIA expansion slot 114 by the PCMCIA interface bus 122.
The PCMCIA host adapter integrated circuit 110 controls and directs communications between the peripherals coupled to the PCMCIA expansion slots 112 and 114 and the system bus 140.
The system bus 140 has a differing number of address and data lines as compared to the address and data line requirements of the PCMCIA interface busses 120 and 122. Data transfers across the system bus 140 are at a different rate than the data transfer to a PCMCIA card 116 or 118. Other control signals, not included on the system bus 140, are also required at the PCMCIA interface in order to adapt to the various needs of differing types of PCMCIA cards that may be inserted. Thus, the PCMCIA interface is very flexible and the PCMCIA host adapter integrated circuit 110 is used to interface differing data and address line requirements having different transfer rates between the system bus 140 and the PCMCIA cards 116 or 118.
The PCMCIA expansion slots 112 and 114 are two typical implementations of sockets, also referred to as slots, into which a PCMCIA card 116 or 118 can be inserted. The PCMCIA standard enables memory and input/output (I/O) devices to be inserted as exchangeable peripherals into electronic devices through a standard interface. A PCMCIA card 116 uses this standard interface, allowing PCMCIA interfaced peripheral devices such as a modem card, a network card, a sound card, a floppy disk drive, a hard disk drive, or other cards to be plugged into the system computer by means of their embodiment in a PCMCIA card 116. This PCMCIA card 116 is plugged into a PCMCIA expansion slot 112 which is coupled to a PCMCIA host adapter integrated circuit 110 within the computer system. The operation of the PCMCIA expansion slot 112 is controlled by the PCMCIA host adapter integrated circuit 110.
In a portable computer system, the graphics controller 134 is included on the motherboard 100. The graphics controller 134 is coupled to the system bus 140 and to the output display used by the portable computer system, by either of the outputs 136 or 138. If the output display used by the portable computer system is a CRT display then the RGB output 136 of the graphics controller 134 is coupled to the display. If the output display used by the portable computer system is a flat-panel display then the flat-panel output 138 of the graphics controller 134 is coupled to the display.
In the systems of the prior art, all communications between a PCMCIA card 116 or 118 and a system component, such as the CPU 126 or the graphics controller 134, take place over the host system bus 140. Therefore, if a PCMCIA card 116 or 118 requires communications with the output display used by the system, it is necessary to communicate to the output display over the host system bus 140. This communication over the host system bus 140 occupies the host system bus 140 and slows down communications between other system components. Also, by requiring communications between a PCMCIA card 116 or 118 and the output display to take place over the host system bus 140, the systems of the prior art require the major system components to be active, thereby drawing power from the battery or other power source, even when they may not be required by the system. What is needed is a method to couple a multimedia type PCMCIA peripheral card over a standard PCMCIA interface. What is further needed is a PCMCIA host adapter integrated circuit which will couple a multimedia type PCMCIA peripheral card directly to the graphics controller, thereby bypassing the host system bus and allowing the host system bus to simultaneously be utilized for communications between other system components.